Câu hỏi:

This is especially worrying when there are about 3,000 plants with values as medicines against cancer, AIDS, heart disease and many other sicknesses.

Read the passage below carefully, and then choose the best answer

Conservation conflicts arise when natural-resource shortages develop in the face of steadily increasing demands from a growing human population. Controversy frequently surrounds how a resource should be used, or allocated, and for whom. For example, a river may supply water for agricultural irrigation, habitat for fish, and water-generated electricity for a factory. Farmers, fishers, and industry leaders vie for unrestricted access to this river, but such freedom could destroy the resource, and conservation methods are necessary to protect the river for future use.

Conflicts worsen when a natural resource crosses political boundaries. For example, the headwaters, or source, of a major river may be located in a different country than the country through which the river flows. There is no guarantee that the river source will be protected to accommodate resource needs downstream. In addition, the way in which one natural resource is managed has a direct effect upon other natural resources. Cutting down a forest near a river, for instance, increases erosion, the wearing away of topsoil, and can lead to flooding. Eroded soil and silt cloud the river and adversely affect many organisms such as fish and important aquatic plants that require clean, clear freshwater for survival.

Question: What does “arise” in line 1 mean?

He owns a series of _______ across the US and beyond.

Without plants, most water would run off as soon as it falls, taking away valuable soil.

Select the synonym of the following bold and underlined word in each sentence in the unit

To conserve electricity, we are cutting down on our central heating.

If you don't have anything _______ to say, I'd rather you kept quiet.

He says he'll tell the authorities but it's just an empty ______.